Theresa May. The government is unlikely to accept any Lords amendment to the Brexit bill over a power of veto.
Photograph: Niall Carson/PA

Theresa May will not allow MPs and peers a proper veto over her Brexit deal in case it gives the EU the incentive to offer the UK bad terms, her spokesman has said.

The prime minister believed the UK must not allow the establishment of a process that encouraged EU countries to scupper Brexit, he said on Monday.

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The warning came on the eve of a House of Lords debate about giving MPs and peers a meaningful vote at the end of two years of talks with Brussels. Parliament is currently only being offered a “take it or leave it” vote: accept May’s Brexit deal or leav e the EU with no deal, and trade on World Trade Organisation terms instead.

However, peers are expected to vote on a cross-party basis for parliament to have the power to reject May’s deal and send her back to the negotiating table if it does not like what she has achieved.

Asked why the government would not accept a more meaningful vote, May’s official spokesman said: “The PM believes we should not commit to any process that would incentivise the EU to offer us a bad deal.”

He said any deal that could be rejected by MPs would “give strength to other parties in the negotiation. We believe it should be a simple bill in relation to triggering article 50 and nothing else.”

Downing Street’s position indicates the government will not accept any amendment passed by the Lords in relation to a vote at the end of the two years of negotiations. It is also sticking to its stance of refusing to guarantee the rights of EU citizens living in the UK until a similar guarantee is achieved for UK citizens in the rest of the EU.

The House of Lords voted by 358 to 256 last week in favour of guaranteeing the rights of EU citizens in the UK as part of its scrutiny of the Brexit bill. MPs are likely to reverse that change when the legislation returns to the Commons, and peers are expected to back down after that in order not to block the passage of the bill by the end of March, when May wants to trigger article 50.